Platform ladder



April 1962 H. HARRISON 3,031,028

PLATFORM LADDER Filed Sept. 11, 1959 2 Sheets-Sheet 1 v Q o a w -:3 I

1 o 2' LO (\1 N i I m N 2 I 1 0 Q Q N u INVENTOR T HENRY HARRISONATTORNEYS H. HARRISON April 24, 1962 2 Sheets-Sheet 2 HENRY HARRISON M44ATTORNEYS Sttes This invention relates to a folding platform ladder andmore particularly to a lightweight metallic platform ladder, and is animprovement over my prior United States Patent No. 2,650,014.

This invention is primarily concerned with a folding platform ladderhaving a pair of spaced front legs, each of which has a rear legpivotally secured to it at a position adjacent its upper end in such amanner that the rear legs pivot outwardly and rearwardly relative totheir associated front legs in order to providesan extremely stable yetrelatively uncomplicated lightweight ladder.

Another feature of this invention is to provide a loadbearing platformintermediate the extremities of the front legs, which platform isadapted to pivot downwardly and rearwardly relative to the front legssimultaneously with the aforementioned pivotal motion of the rear legs.

Still another feature of this invention is to provide an auxiliary traywhich is pivotally connected to the upper end of the front legs and maybe readily swung into an operative position to be readily accessible tothe user of the ladder when standing upon the aforementioned platform.

It is an object, therefore, of this invention to provide a foldingplatform ladder having a minimum of parts, which parts are, however,operatively connected together to provide an extremely stable'an'dlightweight support.

It is a further object of this invention to provide a folding ladder inwhich a supporting platform moves simultaneously with a pair ofoutwardly and rearwardly pivoting legs, thus providing an extremelystable lightweight working platform.

These and further objects and advantages will become readily apparent tothose skilled in the art upon reading the following detailed descriptiontaken in conjunction with the appended drawings in which:

FIG. 1 is a rear elevational view of the ladder of the present inventionin its open, or operative, position;

FIG. 2 is a side elevational view of the ladder in the position shown inFIG. 1, showing the auxiliary supporting tray in its operative position;

FIG. 2a is a fragmentary perspective view showing the method of joiningthe step to the front legs;

FIG. 3 is a partial rear elevational view of the ladder of the presentinvention in its closed position;

FIG. 4 is a perspective view of the ladder of the present invention madeof tubular stock and shown in a partially open position; and

FIG. 4a is a fragmentary perspective View showing the connection of thestep to a tubular front leg in the modification shown in FIG. 4.

One embodiment of the folding platform ladder of the present inventionis shown in FIGS. 1 through 3 disclosing a metallic folding ladder inwhich the metal side rail, which may be lightweight steel or aluminum,has a double thickness channel, and in which the step has a doubletriangular tubular cross-section and employs a metal stitchconstruction. The embodiment illustrated in FIG. 4 shows an alternativetype of construction wherein the metal stock comprises round tubularportions, and the metal step comprises a substantially triangulartubular section, which may also be of lightweight steel or aluminum.

Referring now to FIG. 1, the folding platform ladder comprises a pair ofspaced front legs which are preferably integrally joined at their upperends, providing atent a horizontal extension 12 therebetween such thatthe front legs and horizontal extension present the configuration of aninverted U. A horizontal step 14 extends between the lower ends of frontlegs 10 and is secured thereto in any suitable manner as by metalstitches or rivets 16. A second horizontal step 15 is secured to thefront legs 10 about twelve iuches'above step 14. A pair of rear legs 18is pivotally secured at their upper ends, as at A, to the front legs 10,at a position about ten inches above step 15. The axis of pivotalconnection A is inclined with the horizontal so that each of the rearlegs 18 may pivot outwardly and rearwardly relative to its respectivelyassociated front leg 10, to assume the open position shown in FIGS. 1and 2. The particular pivotal construction is best shown and describedin detail in my prior United States patent referred to above.

Disposed beneath the pivotal connection A is a platform 20 which ispivotally connected to the front legs 10, as at B, and extendstherebetween. The platform 20 is provided on its under surface with atransversely extending re-enforcing or stiffening rib Z2 and also hastransverse flanges 214 on its opposite sides. A pair of first links 2.6are pivotally secured at one end thereof, as at C, to the middle ofre-enforcing rib 22 and their opposite ends are respectively pivotallyconnected to rear legs 13, as at D, at a position approximatelytwothirds the length of the leg from its lower end. Each of the firstlinks 26 includes an additional link portion 2 8 which is pivotalllyconnected, as at E, to the flange 24 of platform 20 and may be in theform of a stiff wire, as shown, which lies along link 26 and extendsoutwardly so as to be pivotally connected to the associated rear leg 18,as at D. When the ladder is in an open position, first links 26 andtheir associated link portion 28 provide a support for platform 20 tomaintain it in a horizontal position relative to the surface upon whichthe ladder is situated.

Referring now to FIGS. 3 and 4, it will be seen that by inclining thepivotal axes of the rear legs 18 relative to the front legs 10 and alsoby inclining the pivotal axes of the links 26 with the rear legs 18 in amanner to be described below, an extension of all of the aforementionedpivotal axes will pass through a common point P on the same side of theladder as the associated front leg 10 and rear leg 18 to provide therearward and outward pivotal motion of the rear leg 18 simultaneouslywith the downward and rearward pivotal motion of the platform 20. Forclarification, the pivot points on the right-hand side of the ladder areindicated as A, B, C, D and E; whereas, the pivot points on theleft-hand side of the ladder have been designated as A, B, C, D and E.

Common point P for the right-hand side and common point P for theleft-hand side lie along a line drawn through the pivotal axis BB' ofthe platform 20' relative to the front legs 10. Pivotal axis A of theright-hand rear leg 18 and right-hand front leg 10 is inclined aspreviously described so that an extension thereof passes through point Pand defines the line A-P. The pivotal axis D of the right-hand firstlink 26 and its associated link extension 28 relative to the right-handrear leg 18 is also disposed at an angle so that an extension thereofwill also pass through point P, thus defining a line D- P. Similarly,the pivotal axis E of the right-hand extension link 28 relative toflange 24 of top platform 20 is also inclined so that an extensionthereof will pass through point P and the final line E-P. It will thusbe seen that an extension of all the pivotal axes of the elementsdisposed on the righhand side of the ladder pass through the commonpoint P and, similarly, on the left-hand side of the ladder extensionsof the various pivotal axes define lines A'P', B-P, D-P and EP, all ofwhich converge at the common point P which is on the same line as thepoint P, which line passes through pivot points B and B. It is thisparticular inclination of the pivotal axes which accounts for thesimultaneous rearward and outward pivotal motion of the rear legs 18relative to the front legs and the downward and rearward pivotal motionof platform 20 relative to front legs 10, thus providing an extremelystable lightweight metallic ladder which has a minimum of operatingparts.

An auxiliary tray or support platform 30 is pivotally mounted upon thehorizontal extension 12 of front legs 10, as by the brackets 32, whichare pivotally supported by rivets 34 connected to extension 12. In theconstruction shown in 'FIG. 4, the brackets 32 pivot on rivets 34 whichare set transversely into the downward extension of vertical studs 36,which make rigid connection to extension 12, and may be retained in itby a stud head at their upper ends. When the ladder is to be folded orput in its closed position, tray 30 may be readily pivoted upwardly andforwardly about extension 12 and rivets 34 and then downwardly so thatit depends from extension 12 between front legs 10 (as shown in phantomin FIG. 1).

It will thus be seen that there has been provided by this invention astructure in which the various objects hereinbefore set forth, togetherwith many practical advantages, are successfully achieved. As variouspossible embodiments may be made of the mechanical features of the aboveinvention, all without departing from the scope thereof, it is to beunderstood that all matter hereinbefore set forth or shown in theaccompanying drawings is to be interpreted as illustrative and not in alimiting sense.

I claim:

1. A folding platform ladder comprising a pair of spaced front legsjoined together at their upper ends; at least one horizontal stepjoining said front legs adjacent to and spaced upwardly from their lowerends; a platform pivotally mounted to said front legs above said step; apair of rear legs; single pivot means connecting each of said rear legsdirectly to said front legs above said platform; means to pivot saidrear legs rearwardly outwardly relative to said front legs about asingle pivot axis to an open position while at the same time pivotingsaid platform downwardly rearwardly relative to said front legs to agenerally horizontal position, said means including a pair of firstlinks each pivotally connected at one of its ends to one of said rearlegs respectively, the other end of both of said links pivotallyconnected to the center underside of said platform and providing asupport therefor when said ladder is in said open position; and meansconnecting said first links with at least one side of the platform.

2. The structure defined in claim 1 wherein said lastmentioned meansincludes opposed link portions, each of which are pivotally connected atone end to the underside of said platform and fixedly joined at theopposite end to said first link.

3. The structure defined in claim 1 in which the pivotal axis of one ofsaid rear legs and its associated front leg, the pivotal axis of saidplatform with respect to said one front leg and the pivotal axes of thefirst link associated therewith all converge at a common point on thesame side of said ladder as said one front and rear leg.

References Cited in the file of this patent UNITED STATES PATENTS1,817,760 Peters Aug. 4, 1931 2,146,020 Lewis Feb. 7, 1939 2,650,014Harrison Aug. 25, 1953 FOREIGN PATENTS 490,356 Italy Feb. 8, 1954503,767 Canada June 22, 1954 1,103,090 France May 18, 1955

